won't start help
Thread Starter
Advanced
Joined: Apr 2009
Posts: 84
Likes: 0
From: Overland Park Kansas
won't start help
I know this is my Corvette site but my son is having problems with his F ormula. It died on him and just won't start. It turns over and comes real close to an idle but just won't stay running. It does shoot a small flame out of the intake after a few seconds of turning the motor over but thats about it.
Any Ideas? You guys have been such a great help for me in the past that I though you may have an idea.
Any Ideas? You guys have been such a great help for me in the past that I though you may have an idea.
Instructor
Joined: Mar 2009
Posts: 140
Likes: 0
From: Coquitlam BC, Canada
Since no answer I will assume its a carb. carburetor backfire is caused by four possibles problems.
1. The ignition timing fires the spark before the intake valve is closed. (The distributor timing is very far off or the wires to the spark plug are in the wrong order or arcing is occurring between wire or posts on the cap.).)
2. The cam timing is has the intake valve open at the wrong time. (The belt or chain has slipped.)
3. The intake valve is leaking badly. (Cracked, burned, bent, or very far out of adjustment intake valve)
4. The exhaust valve on one cylinder is not opening, (damaged valve train on the exhaust side with the intake working normally.)
1. The ignition timing fires the spark before the intake valve is closed. (The distributor timing is very far off or the wires to the spark plug are in the wrong order or arcing is occurring between wire or posts on the cap.).)
2. The cam timing is has the intake valve open at the wrong time. (The belt or chain has slipped.)
3. The intake valve is leaking badly. (Cracked, burned, bent, or very far out of adjustment intake valve)
4. The exhaust valve on one cylinder is not opening, (damaged valve train on the exhaust side with the intake working normally.)
Le Mans Master
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
That would be an LT1 with the opti spark distributor. The symptoms you describe are typical of an opti failure, but he really should do other checks first before just throwing parts at it. Is it getting spark to the plugs and what is the fuel pressure? Also a leak down test to be sure the injectors aren't leaking would be a good idea. Again, is it throwing any codes?
Thread Starter
Advanced
Joined: Apr 2009
Posts: 84
Likes: 0
From: Overland Park Kansas
I don't know if it is throwing any codes because we don't have a way to check it. He is running up to buy a fuel guage right now and we will see what the pressure is. What should I be looking for? 40 pluss pounds?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Advanced
Joined: Apr 2009
Posts: 84
Likes: 0
From: Overland Park Kansas
That would be an LT1 with the opti spark distributor. The symptoms you describe are typical of an opti failure, but he really should do other checks first before just throwing parts at it. Is it getting spark to the plugs and what is the fuel pressure? Also a leak down test to be sure the injectors aren't leaking would be a good idea. Again, is it throwing any codes?
Le Mans Master
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
The backfiring out of the intake is sure to be a timing issue, which in an LT1 almost has to be a bad opti spark.
How about some of the other LT1/4 guys chip in here????
Thread Starter
Advanced
Joined: Apr 2009
Posts: 84
Likes: 0
From: Overland Park Kansas
Yes, that is too easy. A MAF code would not keep it from starting. Turn key on and fuel pressure goes to 40 psi, right? Good! Then turn key off and does it hold the pressure? If yes the fuel system is likely all good. Only thing we don't know for sure is if the injectors are firing.
The backfiring out of the intake is sure to be a timing issue, which in an LT1 almost has to be a bad opti spark.
How about some of the other LT1/4 guys chip in here????
The backfiring out of the intake is sure to be a timing issue, which in an LT1 almost has to be a bad opti spark.
How about some of the other LT1/4 guys chip in here????
Instructor
Joined: Mar 2009
Posts: 140
Likes: 0
From: Coquitlam BC, Canada
I just read a very long and very detailed write up about the opti spark at http://www.gmhightechperformance.com...ing/index.html . Try reading some of it to better understand your distributor, it sure boggled my brain. At the very end it gives you reasons for opti spark failure:
Is Your Opti-Spark Failing?
LT1 owners have dealt with the Opti-Spark distributor for 11 years now, but there is still much confusion regarding the causes and symptoms of a failing unit. Tapping into the PCM with a scan tool is a good way to start, but sometimes no codes will be set. Before diving into the Opti-Spark, be sure to verify that your grounds are good and the coil and wires are not the source of the problem, as they are much easier to change.
Symptoms:
* Car suddenly dies and won't restart
* Starts but immediately dies
* Extended cranking to start
* Rough idle
* Sputtering
* Backfiring
* Trouble reaching higher rpm
* Black smoke from exhaust
* Poor performance with car warmed up
* Weak plug wire spark
* Codes 16, 36, and 42 may be set
Is Your Opti-Spark Failing?
LT1 owners have dealt with the Opti-Spark distributor for 11 years now, but there is still much confusion regarding the causes and symptoms of a failing unit. Tapping into the PCM with a scan tool is a good way to start, but sometimes no codes will be set. Before diving into the Opti-Spark, be sure to verify that your grounds are good and the coil and wires are not the source of the problem, as they are much easier to change.
Symptoms:
* Car suddenly dies and won't restart
* Starts but immediately dies
* Extended cranking to start
* Rough idle
* Sputtering
* Backfiring
* Trouble reaching higher rpm
* Black smoke from exhaust
* Poor performance with car warmed up
* Weak plug wire spark
* Codes 16, 36, and 42 may be set
Thread Starter
Advanced
Joined: Apr 2009
Posts: 84
Likes: 0
From: Overland Park Kansas
I just read a very long and very detailed write up about the opti spark at http://www.gmhightechperformance.com...ing/index.html . Try reading some of it to better understand your distributor, it sure boggled my brain. At the very end it gives you reasons for opti spark failure:
Is Your Opti-Spark Failing?
LT1 owners have dealt with the Opti-Spark distributor for 11 years now, but there is still much confusion regarding the causes and symptoms of a failing unit. Tapping into the PCM with a scan tool is a good way to start, but sometimes no codes will be set. Before diving into the Opti-Spark, be sure to verify that your grounds are good and the coil and wires are not the source of the problem, as they are much easier to change.
Symptoms:
* Car suddenly dies and won't restart
* Starts but immediately dies
* Extended cranking to start
* Rough idle
* Sputtering
* Backfiring
* Trouble reaching higher rpm
* Black smoke from exhaust
* Poor performance with car warmed up
* Weak plug wire spark
* Codes 16, 36, and 42 may be set
Is Your Opti-Spark Failing?
LT1 owners have dealt with the Opti-Spark distributor for 11 years now, but there is still much confusion regarding the causes and symptoms of a failing unit. Tapping into the PCM with a scan tool is a good way to start, but sometimes no codes will be set. Before diving into the Opti-Spark, be sure to verify that your grounds are good and the coil and wires are not the source of the problem, as they are much easier to change.
Symptoms:
* Car suddenly dies and won't restart
* Starts but immediately dies
* Extended cranking to start
* Rough idle
* Sputtering
* Backfiring
* Trouble reaching higher rpm
* Black smoke from exhaust
* Poor performance with car warmed up
* Weak plug wire spark
* Codes 16, 36, and 42 may be set
Any other suggestions?
Thread Starter
Advanced
Joined: Apr 2009
Posts: 84
Likes: 0
From: Overland Park Kansas
Well, I changed the OPTI and the Mass Air flow with no change at all. The starange thing is that the car fits all the thing you posted above for the OPTI. The car did suddenly dien and not start, even the blak smoke as we are trying to start it.
Any other suggestions?
Any other suggestions?
Now I have changed the TPS as well and the car still won't start.
Le Mans Master
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
You are getting nice bright spark at the plugs, right? Fuel pressure was good and you are getting backfire out of the intake, right? Getting spark (at the right time) and fuel, plus compression should be all it needs to start.
Are you getting a gas smell when cranking it?
What did it do when it died on your son? Had he just gotten gas? Any smoke, noises, etc.?
Are you getting a gas smell when cranking it?
What did it do when it died on your son? Had he just gotten gas? Any smoke, noises, etc.?
Thread Starter
Advanced
Joined: Apr 2009
Posts: 84
Likes: 0
From: Overland Park Kansas
You are getting nice bright spark at the plugs, right? Fuel pressure was good and you are getting backfire out of the intake, right? Getting spark (at the right time) and fuel, plus compression should be all it needs to start.
Are you getting a gas smell when cranking it?
What did it do when it died on your son? Had he just gotten gas? Any smoke, noises, etc.?
Are you getting a gas smell when cranking it?
What did it do when it died on your son? Had he just gotten gas? Any smoke, noises, etc.?
The only backfire is when I first turn it over and it is very little. Then it just rotates with nothing. If I peddle it a few times I can get it to backfire again.
Thread Starter
Advanced
Joined: Apr 2009
Posts: 84
Likes: 0
From: Overland Park Kansas
Pluss the fuel gauge shows 40 pluss pounds and it holds.
I was reading a few other threads looking for answers and some people had injector shorts. They would take the injectors off one by one and try to start the car. Do ya think that may be it.
I have taken 3 days off work and have done nothing but work on this car. Thanks for the help and advice.
